You pop off the rear bench seat, and then pry up the cover plate over the tank access. There is an electrical harness you disconnect. Then there are bolts you will remove to get to the thing, as mentioned above. But make sure you clean that area well as you don't want crud falling into your tank.
Any reason you believe you need to change it?
Not likely to be the filter. Your O2 sensors may be going out, causing a rich mixture, the catalytic converter may be going out, issues with the injectors, dirty air filter, bad MAF sensor, poor spark from the plugs, low air pressure in the tires... those are more likely to be the case. What is "bad"? What are you getting, and how are you calculating it?bad gas mileage, maybe my filter has to much dirt ?